Drill bit for horizontal directional drilling

ABSTRACT

A bit body for a drill bit for horizontal directional drilling includes a pair of legs and a small wedge member disposed between the pair of legs. A roller cone is rotatably mounted to each bearing shaft extending from a respective leg. The roller cones support full coverage cutting structures. A center jet nozzle is configured to direct drilling fluid between the pair of roller cones. A stabilizer member maintains an upright drilling position of the drill bit within the borehole.

PRIORITY CLAIM

This application claims priority to U.S. Provisional Application for Patent Ser. No. 61/937,221, filed on Feb. 7, 2014, and entitled “Horizontal Directional Drilling Drill Bit With Improved Directional Control,” the disclosure of which is hereby incorporated by reference.

TECHNICAL FIELD

The present invention relates generally to bits for drilling a borehole, and more particularly to a drill bit for horizontal directional drilling (HDD) with improved directional control.

BACKGROUND

In horizontal directional drilling (HDD) (also known as trenchless drilling), rock drill bits, both rolling cone and fixed cutter, are used to drill generally horizontal holes in the earth. In many cases, these “trenchless holes” are drilled under rivers, roads, or other developed areas. Thus, the bit is directionally controlled or steered underneath or around these obstacles. Sometimes the bit encounters and is steered around obstacles including power lines, water mains, and other obstacles in drilling the horizontal hole. The ability to accurately and reliably steer the bit facilitates successful project completion. Boreholes formed with directionally controlled drill bits are used to route underground sewer lines, water lines, and fiber optic cables, and the like.

Reference is made to FIG. 1, which illustrates a face of conventional three cone bit 5 that includes three cones 10 a, 10 b, and 10 c, each supporting multiple cutters 11. The cutters 11 are arranged in intermeshed rows. Each cone is associated with a drilling fluid nozzle 7 a, 7 b, and 7 c. One embodiment of forming the three cone bit 5 is to weld the components as shown and described in U.S. Pat. No. 4,414,734 to Atkinson, which is hereby incorporated by reference.

To transform the three cone bit 5 into a bit that is more suitable for HDD, cone 10 a including the pin to which it is rotatably mounted may be removed. In the space created by the removal of the cone and the pin, a push plate (not shown) is installed. The push plate provides a lever to push the bit in the desired direction and maintain balanced drilling with the two remaining intermeshed cones 10 b, 10 c.

Of course, removal of cone 10 a, also removes its rows of cutters 11. This often results in uncut rings of formation forming on the borehole bottom. For the purposes of this disclosure, which contemplates horizontal drilling, the borehole bottom refers to the undrilled portion of the borehole which the bit will encounter upon continued drilling, and the sidewall of the borehole refers to the sidewalls that are generally perpendicular to the borehole bottom. For example, if cone 10 a is removed the result may be an outer uncut ring 12 and an inner uncut ring 13 corresponding to the respective rows of cutters of the removed cone 10 a. This uncut borehole bottom is known in the drilling industry to reduce rate of penetration and cause lateral bit instability (also referred to as off center running), which can result in reduced steerability of the bit.

In some horizontal drilling operations, a center jet nozzle 14 is disposed substantially on the axis of rotation 15 of the bit 5. The center jet nozzle 14 directs drilling fluid generally along the bit rotation axis 15 such that the drilling fluid impinges on the borehole bottom where it may remove sticky formation. In other operations, the center jet nozzle 14 is modified such that the drilling fluid flow impinges on the rolling cones 10 b, 10 c where it may remove sticky formation or rock cuttings from the cones themselves. In still other drilling operations, one or more of the nozzles 7 a, 7 b, and 7 c is plugged to cause the drilling fluid to flow to an open nozzle where it can be controlled to fluidly erode the formation in a desired direction of advancement of the bit.

Directional control and rate of penetration of drill bits used for horizontal directional drilling may still be improved.

SUMMARY

A bit body for a drill bit for horizontal directional drilling includes a pair of legs and a small wedge member disposed between the pair of legs. A roller cone is rotatably mounted to each bearing shaft extending from a respective leg. The roller cones support full coverage cutting structures. A center jet nozzle is configured to direct drilling fluid between the pair of roller cones.

According to an alternate embodiment, the bit body includes a large wedge where the included angle of the large wedge member is greater than the included angle of the small wedge member. The large wedge member may be welded to the legs on one side of the bit body, and the small wedge member may be welded to the legs on the other side of the bit body.

According to a further alternate embodiment, a stabilizer member extends from the bit body and is configured to maintain a drilling orientation of the drill bit within a borehole. The stabilizer may include wear protection elements applied to its outer surface.

An alternate embodiment of a bi-cone drill bit for horizontal directional drilling according to the teachings of the present disclosure includes an extended nozzle that extends between the two legs and directs a stream of drilling fluid to be concentrated near a borehole bottom to fluidly erode a formation to aid in steering the bi-cone bit.

One technical advantage to embodiments taught by the present disclosure is a bi-cone bit employing full coverage roller cones to ensure that the borehole bottom is fully addressed by the cutting elements supported by the roller cones such that rings of uncut formation are not left due to the removal of one of three intermeshed roller cones.

A further technical advantage includes a bi-cone drill bit for use in horizontal directional drilling that employs conventionally fabricated legs of a three cone bit including full sized bearings.

Still a further technical advantage includes a bi-cone bit that is configured to fluidly erode an earth formation at a transitional zone of a borehole located between a borehole sidewall and a borehole bottom while maintaining a generally upright drilling position of the drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and the advantages thereof, reference is now made to the following brief description, taken in connection with the accompanying drawings and detailed description, wherein like reference numerals represent like parts, in which:

FIG. 1 illustrates a face of a conventional three cone roller cone drill bit;

FIG. 2A illustrates a body of a bi-cone bit for use in horizontal directional drilling according to an embodiment of the present disclosure;

FIGS. 2B and 2C are perspective views of wedge members forming the bit body of FIG. 2A;

FIG. 3 illustrates a face of the bi-cone bit of FIG. 2A; FIG. 4 is a cross-section of the bi-cone bit of FIG. 2A illustrated in a drilling position within a borehole;

FIG. 5 is a cross section of an embodiment of the large wedge member and a stabilizer member of FIG. 4 with hardfacing material applied to enhance wear resistance;

FIG. 6 is a cross section of an alternate embodiment of the large wedge member and the stabilizer with wear resistant inserts enhancing wear resistance; and

FIGS. 7A and 7B are respectively a face view and a cross-section of an alternate embodiment of a bi-cone bit including an extended nozzle for use in horizontal directional drilling according to the teachings of the present disclosure.

DETAILED DESCRIPTION

Reference is now made to FIGS. 2A-2C. FIG. 2A illustrates a body of a bi-cone bit 16 for use in horizontal directional drilling (“HDD”). The “shirttail” portion of each of two legs 18 a, 18 b is omitted to show details of the body of the bit 16. The omitted shirttail portions include the bearing shafts and the two roller cones that are each rotatably mounted to a respective bearing shaft.

The body of the bi-cone bit 16 includes a small wedge 20 that is disposed between the legs 18 a and 18 b on one side, and a large wedge 22 that is disposed between the legs 18 a and 18 b on the other side. One advantage of the bi-cone bit 16 is that the body includes conventional legs 18 a, 18 b. The legs 18 a, 18 b are conventionally formed as machined steel forgings, and according to certain embodiment are stock parts used in the manufacturing of conventional three cone bits. As such, each leg 18 a, 18 b includes a nozzle 24 a, 24 b, each of which is blocked by a plug 26 a, 26 b in order to direct full drilling fluid flow through a center jet nozzle 28 to steer the bit 16, as described in more detail below with respect to FIG. 4.

With additional reference to FIGS. 2B and 2C, the bit body is formed by welding together the leg 18 a, the small wedge 20, the leg 18 b, and the large wedge 22. Specifically, a leg face 30 a proximate the nozzle 24 a is abutted to a large wedge face 32. A leg face 34 a opposite of leg face 30 a is abutted to a small wedge face 36. Similarly, for the other leg 18 b, a leg face 34 b is abutted to a large wedge face 38, and an opposite leg face 30 b is abutted to a small wedge face 40. The components are welded or otherwise joined together to form the body of bi-cone bit 16. In this manner, the small wedge 20 and the large wedge 22 together occupy the space that would otherwise be occupied by the third leg of a conventional three cone bit.

The small wedge 20 has an included angle θ1 sufficient to prevent the cutters of the two cones from striking and interfering with the rotation of the cones, as described in more detail below with respect to FIG. 3. In one embodiment, this included angle is approximately 20°-30°. The large wedge 22 has an included angle θ2 of approximately 120° minus the included angle θ1 of small wedge 20 and is greater than the included angle θ1 of small wedge 20. In the illustrated embodiment, θ1 is approximately 20° and θ2 is approximately 100°.

The small wedge 20 includes a cavity portion 42, and the large wedge includes a cavity portion 44. The small wedge 20 and the large wedge 22 are formed by machining steel forgings similar to the fabrication of the legs 18 a, 18 b. For example, the steel forgings of the small and the large wedges are machined to form threads 46 that enable the bi-cone bit 16 to be coupled to a drill string. Upon forming the bit body, the cavity portions 42 and 44 with the legs 18 a and 18 b, the bit body defines a central plenum through which drilling flows from the surface to the center jet nozzle 28.

Reference is now made to FIG. 3, which shows a face of the bi-cone bit 16. The face includes a cone 46 a rotatably mounted to the bearing shaft extending from leg 18 a and a cone 46 b rotatably mounted to the bearing shaft extending from leg 18 b. In addition, a bottom surface of the large wedge 22 provides a robust location for attaching, adhering, or otherwise implementing a stabilizer 48.

Each cone 46 a, 46 b of the bi-cone bit 16 supports a plurality of cutters 50. The cutters may be PDC cutter inserts that are cone-shaped, dome-shaped, chisel-shaped or any other suitable cutting structure that is known in the art. The cones 46 a, 46 b are full coverage cutter cones because the cutters 50 are positioned at locations over the entire surface of each cone such that the full borehole bottom is addressed by one or more cutters 50 on each of cones 46 a, 46 b. In certain embodiments, the cutters 50 are randomly positioned on the cones. The full coverage cones 46 a, 46 b together apply cutters 50 to the full bottom of the borehole, as opposed to the intermeshed rows of the remaining cones of a modified three cone bit as shown and described with respect to FIG. 1.

As stated above with respect to FIG. 2A, the included angle θ1 of the small wedge 20 is selected such that the full cutter coverage cones 46 a does not interfere with the full coverage cutter cone 46 b. In this manner, full cutter coverage cones 46 a, 46 b are employed instead of cutters formed in intermeshing rows as shown and described above with respect to the three cone bit shown in FIG. 1. In addition, each leg 18 a, 18 b supports a full size bearing for each of cones 46 a, 46 b. According to an alternate embodiment, the large wedge 22 and the small wedge 20 are formed as a single integral steel machined forging.

Reference is now made to FIG. 4, which illustrates a cross section of the bi-cone bit 16 disposed in a drilling position in a generally cylindrical borehole defined by a sidewall 52 that converges through a transitional zone 53 to a borehole bottom 54. The stabilizer 48 extends from the large wedge 22. The stabilizer 48 is generally a wedge-shaped machined steel forging. In some embodiments, the stabilizer is formed integrally with the large wedge 22. In other embodiments, the stabilizer 48 may be welded, brazed, or otherwise attached to a bottom surface of the large wedge 22. A function of the stabilizer 48 is to maintain upright drilling position orientation of the bi-cone drill bit 16 during drilling and during a halt in drilling when the drilling fluid nozzle is employed to fluidly erode the formation to facilitate directional control of the bit 16.

The stabilizer 48 includes generally rounded surfaces to minimize any cutting of the borehole sidewall 52 by the stabilizer 48. Also, the stabilizer 48 is disposed above the bottom 54 of the borehole to ensure that the bottom 54 of the borehole is not addressed and possibly cut by the stabilizer 48. The cutting and drilling action of the bi-cone bit 16 is performed by the cutters 50 supported by the cones 46 a, 46 b (only one cone shown in FIG. 4). During drilling, the stabilizer 48 ensures balanced drilling such that the orientation of the bit in the borehole is maintained by the outer surface of each leg 18 a, 18 b, the outer surface of the large wedge 22, and the stabilizer 48.

The stabilizer 48 also maintains the balance of the bi-cone bit 16 when operating the center jet nozzle 28 to facilitate bit steering. The center jet nozzle 28 receives drilling fluid from the plenum and is configured to direct the drilling fluid between cone 46 a and cone 46 b. In one embodiment, the center jet nozzle 28 is oriented at an angle with respect to the axis of rotation or centerline of the bit. This angle is selected such that the fluid flow impacts the transitional zone 53 between the borehole sidewall 52 and the bottom 54 of the borehole such that formation is eroded and a depression or grove is created, which will aid in steering the bit. For example, the bi-cone bit 16 may be advanced into the earth and rotated about its rotational axis to create the borehole through the cutting action of the cutters 50 supported by the cones 46 a, 46 b. If an obstacle is encountered that the bit is to be steered around, the bit rotation can be halted such that the center jet nozzle 28 is positioned to direct a stream 56 of drilling fluid from the center jet nozzle 28 to erode an area of the borehole in the desired direction to steer the bit 16. A grove is eroded or cavity is eroded in the formation by the drilling fluid stream 56. The bit 16 is then positioned in the grove and bit rotation is restarted such that the bit drills formation in the steered direction.

The center jet nozzle stream 56 is oriented with respect to the circumference of the bit 16 such that the location of impingement of the nozzle stream 56 with the formation is approximately 180° opposed to the stabilizer 48. In this manner, the contact between the sidewall 52 and the stabilizer 48 opposes the force created by the center jet nozzle 28 and maintains the bit in an upright orientation. According to an alternate embodiment, the location of impingement may be 135°-225° opposed to the stabilizer 48. According to an alternate embodiment, the nozzle stream 56 by be angled in a generally forward direction toward cone 46 b or a generally rearward direction toward cone 46 a may be applied to aid the steering of the bi-cone bit 16.

Reference is now made to FIG. 5, which illustrates a cross section of an alternate embodiment of the large wedge 22 and the stabilizer 48. According to the illustrated embodiment, erosion resistance of the stabilizer 48 is enhanced by applying wear resistant material to an outer surface of the large wedge 22 and/or the stabilizer 48 at locations that are particularly susceptible to erosion due to contact with the sidewall 52 of the borehole. For example, a layer of welded hardfacing material 58 is applied to the outer surface of the large wedge 22 and/or the stabilizer 48. The hardfacing material 58 is a deposit of tungsten carbide hard metal. The material is typically pelletized tungsten carbide carried in a welding medium primarily composed of nickel. High heat is used to apply a layer of the hardfacing material 58. According to one embodiment, the hardfacing material 58 may be substantially flush with the outer surface of the large wedge 22.

An alternate embodiment of improving erosion and wear resistance of the large wedge 22 and the stabilizer 48 is shown in FIG. 6. Erosion resistant inserts 60 are press-fit or brazed in a cavity formed in the stabilizer 48. According to one embodiment, the erosion resistant inserts 60 are generally cylindrical tungsten carbide members that are press-fit or brazed into cavities formed in an outer surface of the large wedge 22. The erosion resistant inserts 60 may also be press-fit or brazed into a cavity formed in an outer surface of the stabilizer 48. The wear resistant inserts 60 may provide wear resistance that is superior to the wear resistance of the hardfacing material 58 because of the tendency of the welding medium, typically nickel to break down when drilling highly abrasive rock formations. In other embodiments, the wear resistant inserts 60 may be polycrystalline diamond compact (PDC) inserts, inserts in the form of impregnated diamond slugs, or inserts in the form of impregnated diamond plates. These erosions resistance inserts 60 may be either press-fit or brazed to secure them to the large wedge 22 and/or stabilizer 48 at locations that are susceptible to erosion. In order to press-fit the wear resistant inserts, the holes that receive the inserts must be located at some appreciable distance from an edge in order for the press-fit to function properly and peripherally retain the inserts 60.

According to yet another embodiment to enhance erosion resistance of the large wedge 22 and/or the stabilizer 48, tungsten carbide plates may be brazed to an outer surface of the large wedge 22 and/or the stabilizer 48 similar to the teaching of tungsten carbide plates applied to a leading transitional leg surface of a three cone bit, as disclosed and described in U.S. Patent App. Pub. No. 2014/0299384 by Harrington et al., which is hereby incorporated by reference.

Reference is made to FIGS. 7A and 7B, which illustrate respectively a face and a cross section of an extended nozzle HDD bi-cone bit 61 according to an alternate embodiment of the present disclosure. An extended nozzle 62 extends downward such that it is proximate the borehole bottom 28. The extended nozzle 62 is disposed between cone 46 a and cone 46 b. In some embodiments, the extended nozzle 62 extends from the small wedge 20. In this embodiment, a conduit 64 runs through the small wedge 64 and the extended nozzle 62. The conduit 64 fluidly couples an outlet 66 of the extended nozzle 62 to the plenum.

The extended nozzle 62 allows drilling fluid to be focused at a particular location of the borehole. For example, the outlet 66 of the extended nozzle 62 may be less than about seven times the diameter of the nozzle orifice away from the borehole bottom 28. For example, if the nozzle orifice were 0.5 inches in diameter, then an exit plane of the outlet 66 of the extended nozzle 62 is disposed within about 3.5 inches (7×0.5) above the borehole bottom 54 and oriented toward the transitional zone 53 between the borehole sidewall 52 and the bottom 54 of the borehole. The exit plane is the plane at which the drilling fluid exits the nozzle and begins to form drilling fluid 68 generally in the form of a cone. In this manner, the cone of drilling fluid 68 from the extended nozzle 62 erodes formation and generates a depression or grove, which will aid in steering the bit, as described above with respect to FIG. 4. The extended nozzle 62 is circumferentially oriented on the extended nozzle bi-cone bit 61 such that the location of impingement of the drilling fluid is approximately 180° degrees opposed to the stabilizer 48. According to an alternate embodiment, the location of impingement may be 135°-225° opposed to the stabilizer 48. Also, the nozzle stream 68 by be angled in a generally forward direction toward cone 46 b or a generally rearward direction toward cone 46 a may be applied to aid the steering of the bi-cone bit 61. In certain embodiments, the exit plane of the outlet 66 of the extended nozzle 62 is not parallel with the borehole bottom 54, but rather is angled to focus the drilling fluid even more directly toward the transitional zone 53 between the borehole wall 52 and the borehole bottom 54.

According to the teaching of the present disclosure, the embodiments disclosed herein resolve problems of lateral instability related to excessive uncut borehole bottom, and thereby increase the rate of penetration and increase lateral stability and also reduce off center running The directional control of a bi-cone bit used for horizontal directional drilling is substantially improved. Additionally, the disclosed embodiments provide improved steerability by providing efficient hydraulic energy focused on a selected portion of the borehole to erode formation and aid in directional control of the HDD bit.

The foregoing describes only some embodiments of the invention(s), and alterations, modifications, additions and/or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive. 

What is claimed is:
 1. An earth boring drill bit, comprising: a bit body comprising a pair of legs and a small wedge member disposed between the pair of legs; a pair of roller cones each rotatably mounted to a bearing shaft extending from a respective leg, the roller cones supporting full coverage cutting structures; and a center jet nozzle configured to direct drilling fluid between the pair of roller cones.
 2. The drill bit of claim 1, wherein the bit body further comprises a large wedge member disposed between the pair of legs circumferentially opposite the small wedge member.
 3. The drill bit of claim 2, further comprising a stabilizer member extending from the large wedge member and being configured to maintain a drilling orientation of the drill bit within a borehole.
 4. The drill bit of claim 3 wherein the drilling fluid nozzle directs drilling fluid at an angle away from the stabilizer member.
 5. The drill bit of claim 3 wherein the stabilizer member includes a wear resistant element configured to protect an outer surface of the stabilizer member.
 6. The drill bit of claim 5 wherein the wear resistant element comprises a layer of hardfacing material applied to a portion of the outer surface of the stabilizer member.
 7. The drill bit of claim 5 wherein the wear resistant element comprises a plurality of generally cylindrical inserts.
 8. The drill bit of claim 7 wherein the plurality of generally cylindrical inserts includes tungsten carbide inserts.
 9. The drill bit of claim 1 wherein the center jet nozzle is angled to direct drilling fluid to fluidly erode a formation at a transitional zone between a sidewall and a bottom of a borehole.
 10. The drill bit of claim 1 wherein the pair of legs comprises a pair of steel forgings.
 11. The drill bit of claim 1 wherein each one of the pair of legs is a leg of a conventional three cone roller cone bit.
 12. The drill bit of claim 1 wherein the drill bit is a bi-cone bit.
 13. The drill bit of claim 1 wherein an included angle of the small wedge member is 20°-30°.
 14. The drill bit of claim 13 wherein the bit body further comprises a large wedge member disposed between the pair of legs circumferentially opposite the small wedge member, an included angle of the large wedge member being approximately 120° minus the included angle of the small wedge member.
 15. The drill bit of claim 13 wherein the included angle of the small wedge member is approximately 20°.
 16. The drill bit of claim 1 wherein the small wedge member includes a cavity, the cavity defining a portion of a central plenum of the drill bit.
 17. A bi-cone earth boring bit for horizontal directional drilling, comprising a pair of legs separated by a first wedge member disposed on one side and separated by a second wedge member disposed on a second side, the first wedge member having an included angle greater than an included angle of the second wedge member; a bearing shaft extending from each leg; a roller cone rotatably mounted to each bearing shaft, the roller cones supporting a plurality of cutters configured to fully cut a borehole bottom; and a stabilizer member extending from the large wedge member.
 18. The bi-cone earth boring bit of claim 17, further comprising: a center jet nozzle disposed proximate a center of the bi-cone earth boring bit and configured to a direct drilling fluid between the roller cones and toward a transitional zone between a borehole sidewall and the borehole bottom.
 19. The bi-cone earth boring bit of claim 17, further comprising: an extended nozzle extending between the roller cones and having a nozzle orifice and defining an exit plane, the nozzle orifice having a diameter; and wherein the exit plane is configured to be disposed a distance above the borehole bottom, the distance being less than seven times the diameter of the nozzle orifice.
 20. The bi-cone earth boring bit of claim 17 wherein the included angle of the second wedge member is 20°-30° and the included angle of the first wedge member is approximately 120° minus the included angle of the second wedge member.
 21. A horizontal directional drilling drill bit, comprising: a pair of legs separated by a first wedge member disposed on one side and separated by a second wedge member disposed on a second side, the first wedge member having an included angle greater than an included angle of the second wedge member; a plurality of roller cones, each roller cone coupled to a respective one of the pair of legs; a stabilizer member extending from the first wedge member, the stabilizer member supporting hardfacing material or wear resistant inserts or both; and a drilling fluid nozzle configured to direct drilling fluid to fluidly erode a formation at a transitional zone between a borehole sidewall and a borehole bottom.
 22. The drill bit of claim 21 wherein the drilling fluid nozzle is an extended nozzle extending between the roller cones and having a nozzle orifice and defining an exit plane, the nozzle orifice having a diameter; and wherein the exit plane is configured to be disposed a distance above the borehole bottom, the distance being less than seven times the diameter of the nozzle orifice.
 23. The drill bit of claim 22 wherein the distance is between one and four inches.
 24. The drill bit of claim 21 wherein the drilling fluid nozzle is a center jet nozzle disposed proximate a rotational axis of the drill bit and being configured to direct drilling fluid between the roller cones. 